1. Field of the Invention
This invention relates to components for easy construction of structures, and more particularly to tubular frame components for easy construction of strong, externally smooth structures
2. Discussion of the Background
It has long been known that combinations of tubes and connectors can be used to quickly create framework structures such as jungle-gyms and tents. By connecting tubes at their ends, the frameworks for geodesic domes, furniture and display cases can be created.
In a typical system, that of U.S. Pat. No. 5,169,258 (issued to Raynak), the fittings have cylindrical pins protruding from a semi-spherical body. PVC pipes are plugged onto the pins and so used to form even large structures such as the framework of a house. Other similar patents (U.S. Pat. No. 4,273,462 to Fukuchi; U.S. Pat. No. 4,242,969 to Checkwood et al.; U.S. Pat. No. 4,187,649 to Chaffee; U.S. Pat. No. 3,074,203 to Paksy) use various types of connectors to assemble pipes into larger structures such as display cases and coffee tables.
Other patents have used the same general technique with tubes having a square cross section: U.S. Pat. No. 5,820,289 to Kern et al.; U.S. Pat. No. 5,451,115 to Sayres; U.S. Pat. No. 4,368,998 to Pestoor; and U.S. Pat. No. 3,736,035 to Brown et al. There are certain advantages all such systems possess.
All the references listed above combine flexibility of design with ease of construction. By altering the arrangement of connectors and tubes new structures can be designed with great ease. Construction is also very easy, as the standardized connectors (also called fittings, joints or corners) and tubes (also called pipes or frame members) can be manufactured with great economy and put together quickly, with few or no special tools and by personnel having little experience or training. If the structure needs to be later modified, most such designs allow for easy disassembly and reassembly in a new configuration.
Such structures also tend to have certain general weaknesses. The completed structure is not a shell or panel type of structure and therefore stress, strain, and torsion, are all applied directly and fully at the couplings between fittings and pipes. Repeated cycles of use, or repeated applications of force to the completed structure, quickly deform the couplings and the structure tends to fall apart shortly.
Most of the references cited above do not refer to paneling. Those that do refer to paneling or shelves (for example, Brown and Kern) teach the panel or shelf as something requiring support from the tubular cross members. None of the references offer means for reducing the forces induced in the couplings, and none offer the panels as structural support for the framework. Finally, none of the references disclose structure allowing a flush, smooth tangential connection of paneling and circular section framework. In each case, paneling is taught as being radial to the tubular framework, not tangential.
One attempt to make the panels bear a structural burden can be seen in U.S. Pat. No. 5,647,650, issued Jul. 15, 1997 to Daugherty et al. In this case, the tubular support structures (there are no cross beams) have wide flanges which grip the end of a wall, thus helping to distribute imposed forces. The panels may be angled, rather than directly radial, but the wide flanges necessarily protrude from the completed structure. More importantly, that system is not actually modular, as it lacks fittings or connectors to connect the tubes, thus flexible design and assembly in to a wide variety of structures is not possible. The modular tubes of Daugherty (""650) are vertical members only, held in place on a base plate which may form the bottom of a wheeled cabinet. A complete framework, as such, is not present, and as with the above references, no structure is disclosed allowing a smooth, flush tangential connection of the paneling and the framework.
The invention consists of several components which interlock to form a strong, externally smooth structure. Tubes, rods or frame members are connected at their ends by fittings (also called joints or corners). Alternatively ends and fitting joints are part of the rod or frame member and attach to other ends or fitting of cross members. The fittings have faces which are symmetrical in external form and size the external surface of the tubes, rods or frame members, thus providing flush, smooth joints. The invention also has a panel which attaches to the framework. The panel connects to the side of the framework, on the plane defined by tangents of the tubes, rods or frame member rather than in the plane defined by the center axes of the tubes, or members, or some plane in between.
In order to provide a smooth, flush fit between the panel and the framework, a recess is provided in the frame member and fittings to accept the panel. The recess runs in a continuous groove along the length of a frame member along the matching faces of the fitting or ends, and then along the length of a second frame member matched to its end of the fitting. The recesses may engage the entire periphery of the panels, by traversing from tube to fitting around the entire periphery of the panel. They may also be discontinuous.
The recess forms a partial chordal section of the frame member if one were to view a circular cross section of a tube: one surface of the panel fits chordally into the tube""s surface while an edge of the panel is substantially radial to the tube. In other embodiments the tangent chord is formed by the panel coming from the curved outer surface of the frame member, making a smooth transition from the panel to the frame member. Thus the recess has a first surface which is parallel to the panel""s exterior surface, which will be referred to herein as the bottom of the recess. The recess also has one surface which is substantially normal to the panel""s exterior surface, which will be referred to herein as the peripheral wall of the recess. The thickness of the panel is equal in depth to the recess as measured from the exterior surface of the tube or member to the bottom along the peripheral wall. The panel""s exterior surface will thereby join smoothly to the member""s exterior surface, and to the exterior surfaces of the fittings, without any step, gap, or discontinuity.
The fasteners used to hold the various components together may be disposed within the completed structure, resulting in an entirely smooth exterior. This requires that three different properties of the edge of the panel be shaped to exactly mate with the recess. First, the edge outline is the shape of the panel in two dimensions not including thickness. The edge outline may be a perfect square, a square with rounded corners, or other shapes. Also, the panel may not be wholly planar, instead being contoured in three dimensions, for example as a nose-cone or other bulbous shape.
The second property, the edge thickness, is generally equal to the depth of the recess. However, edge thickness may be less than the depth of the recess if, for example, the peripheral wall is situated at an angle to the radius of the tube, rather than being exactly radial. The balance of the panel is also usually, but not necessarily, the same thickness as the edge thickness.
Finally, the edge cross section is viewed in the plane normal to the surface of the panel and perpendicular to the axis of the tube. The shape of the edge cross section may either vary or be constant around the entire periphery of the panel. In one embodiment, the edge cross section will be complementary to the cross section of the recess in the plane perpendicular to the axis of the tube. The complementary edge cross section and recess cross section provide a snug and continuous contact between the panel edge and the recess. The three different properties of the edge of the panel thereby create the three dimensional shape exactly matching the space defined by the recess.
Smooth exteriors are beneficial in applications in which streamlining is important, such as trailers, or where cleanliness is important. Smooth exteriors are also useful any time projections on a structure would be disadvantageous, for example when projections might catch on external machinery. The form is also eye-pleasing.
The structure""s interior will not be smooth or flush; because the panels are tangential to the exterior of the frame member, a cavity between the panel and the fittings and tubes of the framework is formed in the interior. There may also be visible on the inside of the structure, apparatus for securing the panels to the framework. For example a linear bead of welded metal may be used to secure the panel to the tubes and fittings. Stud/bolt and bracket combinations may also be used. This less eye-pleasing interior can be easily modified by making a structure with panels tangential to both sides of the framework. This embodiment not only allows both the structure""s interior and exterior to be smooth, but also greatly strengthens the structure. The interior of the assembled structure should not be confused with the xe2x80x9ctube interior,xe2x80x9d the interior of any tube components.
More importantly, the panel is a planar load bearing member. Most fitting and tube structures must absorb all imposed forces at the connection of cross pieces and corner, thereby allowing small forces to generate large torques. In contrast, the present invention takes advantage of the panel to provide a distributed load bearing structure: a monocoque shell. A load imposed on a frame member at the top of the structure will not be primarily transmitted to the fittings at the end of the frame member, but rather largely to the panel edge by the opposing peripheral wall of the tube""s recess. The panel will in turn transmit the force to the recess of the tube on its far side, and so on until the force is absorbed.
It is therefore one object of the invention to provide an improved structural system allowing use of structural panels with easy assembly.
It is another object of the invention to provide a frame member and fitting framework which allows speedy assembly, yet which reduces the forces induced in the couplings between tubes and fittings.
It is another object of the invention to provide a structural system which allows easy assembly of a strong monocoque structure.
It is another object of the invention to provide a structural system allowing easy assembly of strong structures able to withstand numerous cycles of use.
It is another object of the invention to provide a structural system allowing use of structural panels yet allowing easy manufacture of the system components.
It is yet another object of the invention to provide a structural system allowing a smooth, flush joint between panels and elements of a tubular framework.
It is yet another object of the invention to provide a structural system allowing easy assembly of strong, streamlined structures.
It is yet another object of the invention of provide a structural system allowing a tangential joint between panels and elements of a framework.
It is yet another object of the invention to provide a method of constructing a frame member and fitting structure having structural panels and a smooth exterior.
It is yet another object of the invention to provide a structural system allowing construction of a structure which has no projecting flanges, fittings, or fasteners.